1. Technical Field
This invention relates generally to apparatus and methods for controlling robots or other similar devices. This invention relates particularly to apparatus and methods that a human operator may use for manually controlling a robot arm or other slave devices. Still more particularly, this invention relates to establishing a kinesthetic coupling between the operator and the robot by means of a manual control input device.
2. Background Art
Although robotics is a rapidly developing field, for decades to come there will be many applications and tasks that are far too complex and unstructured to be performed completely by unsupervised autonomous robots. Therefore, the need for direct human supervision and control of advanced robotic systems will continue. This is true both in space applications and in terrestrial applications, such as undersea exploration, remote defense technologies, and various tasks in the nuclear industry. Often it is necessary to have the human operator physically removed from the actual work site, remotely supervising and guiding the robot in the performance of a difficult or dangerous task. Remote manipulation is essential when barriers, distances or environmental hazards separate the human operator from a task to be performed. One of the key problems facing the designers of human-supervised robotic systems is how to interface human operators with these complex remotely operated machines.
Researchers have worked for many years to develop a useful, intuitive interface between human operators and teleoperated machines. In general, a teleoperator is any device that allows humans to manipulate or examine objects and environments remotely. In the late 1970's, J. K. Salisbury collaborated with A. K. Bejczy of the Jet Propulsion Laboratory to develop a force reflecting master for use in bilateral control of teleoperated systems. Reference is made to Bejczy and Salisbury, Kinesthetic Coupling Between Operator and Remote Manipulator, Proceedings of the International Computer Technology Conference, ASME, August, 1980 and to Bejczy and Salisbury, Controlling Remote Manipulators Through Kinesthetic Coupling, Computers in Mechanical Engineering, July, 1983, pp. 48-60, which describe the work of Salisbury and Bejczy. A manual hand controller input device is presently necessary for a human operator to control teleoperated machines.
A hand controller generally includes a plurality of structural members connected at joints that permit relative movement of the members as an operator moves a handgrip. As the operator moves the handgrip around in a defined work envelope, a control computer reads signals indicative of movements of each member and calculates the position of the handgrip relative to a defined reference. The computed information is then used to control the corresponding motion of the remote manipulator. The signals indicative of movements of the handgrip are typically transmitted to the control computer by sensors included in the hand controller.
Forces and torques applied by a telemanipulator in a remote work site may be sensed by various techniques. For example, a force/torque sensor may be mounted on the end of the telemanipulator to directly measure the forces and torques encountered. Each axis on the hand controller may have a motor associated therewith, which means that a six degree of freedom system has six motors.
The measured values of the forces and torques are transmitted to a control computer that is connected to the hand controller. The control computer transforms the force and torque signals into appropriate pulse width modulated signals to drive the six motors of the hand controller and reproduce a scaled representation of the forces and torques encountered in the remote work site. The human operator thus appears to feel the forces and torques exerted by the environment on the manipulator.
Forces and torques may be determined by a position disparity technique, which relies upon the relative disparity between the position commanded and the actual position achieved by the remote manipulator. Therefore, if the manipulator strikes a fixed object in the environment, there is a corresponding difference in the commanded position and the actual position of the manipulator. A force proportional to the magnitude of the disparity is generated in the hand controller.